This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-320680, filed Oct. 20, 2000; No. 2001-098182, filed Mar. 30, 2001; No. 2001-098183, filed Mar. 30, 2001; and No. 2001-321448, filed Oct. 19, 2001, the entire contents of all of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of manufacturing a semiconductor device having an insulation film formed by a coating technique.
2. Description of the Related Art
As wiring dimensions are changing smaller with a miniaturization of a semiconductor element, a parasitic capacity is increasing. In recent years, an increase in inter-wiring capacity of such type have a great effect on an operating speed of the device.
Conventionally, a silicon oxide film formed by a thermal CVD or plasma CVD has been employed as an interlayer insulation film of the semiconductor device. However, in recent years, in order to reduce an interlayer capacity, it is required to apply a low permittivity film such as an organic silicon oxide film or an organic film without silicon to the interlayer insulation film.
A relative dielectric constant of a general silicon oxide film (Pxe2x80x94SiO2) obtained by conventional plasma CVD is about 4.1. In addition, the relative dielectric constant of a silicon oxide film obtained by adding fluorine (P) to the silicon oxide film (Pxe2x80x94SiO2) is 3.3. This is a lowest limit of the relative dielectric constant of the insulation film formed by the thermal CVD or plasma CVD.
In contrast, an interlayer insulation film with about 2.4 to 2.8 in relative dielectric constant can be achieved by using a low relative dielectric constant film such as the organic silicon oxide film. However, in actuality, there are a variety of problems in practical use of these low relative dielectric constant films. As one of such serious problems, there can be exemplified a lower mechanical strength of the film. If the mechanical strength of the film is low, a crack occurs with the film during film forming and after film forming or an exfoliation of the film occurs during a CMP process. If such the crack or exfoliation occurs, it is difficult to produce a wire with its high reliability.
Most of the low relative dielectric constant film such as the organic silicon oxide film is formed by a process using coating. In the process, for instance, a liquid-like raw material called vanish in which a precursor of a substance comprising the low relative dielectric constant film is dissolved in solvent is applied on a substrate to be treated, and then, the liquid-like raw material is heated, thereby ensuring evaporation of a solvent volatile and bridge of the precursor. The precursor used here indicates a series of substances that is at a stage before a target product.
Now, the sequence of a process for forming an insulation film using a conventional coating technique will be specifically described below by way of example of a polymethyl siloxane film (organic silicon oxide film). An outline of the process is as follows (step xe2x80x9caxe2x80x9d to xe2x80x9ccxe2x80x9d).
Step xe2x80x9caxe2x80x9d: Applying of a vanish.
Step xe2x80x9cbxe2x80x9d: Heat treatment at about 80 to 200xc2x0 C. and for about one minute.
Step xe2x80x9ccxe2x80x9d: Heat treatment at about 400 to 450xc2x0 C. for about 30 to 60 minutes.
The above process will be described in detail. First, a vanish obtained by dissolving polymethyl siloxane in solvent is applied with a spin coating technique using a coater, and a coat film is formed (step xe2x80x9caxe2x80x9d). Next, the substrate is heated at a temperature of 80 to 200xc2x0 C. for one minute (step xe2x80x9cbxe2x80x9d). Finally, the substrate is heated at a temperature of 400 to 450xc2x0 C. for 30 minutes (step xe2x80x9ccxe2x80x9d), and a polymethyl siloxane film is obtained.
In the above sequence (steps xe2x80x9caxe2x80x9d to xe2x80x9ccxe2x80x9d), the step xe2x80x9cbxe2x80x9d is responsible for a treatment for solidifying a film material by solvent evaporation, and the step xe2x80x9ccxe2x80x9d is responsible for a treatment for forming a bridge between polymethyl siloxane molecules, respectively.
The characteristics of the polymethyl siloxane film formed by the process are described below.
In general, although such the insulation film is low in relative dielectric constant, the density is low, and/or a void concentration is high. Thus, the polymethyl siloxane film has a defect that its mechanical strength is low.
Further, when such an insulation film with low mechanical strength is formed by the above described process, there arises a problem that a crack at predetermined thickness or more occurs. The thickness of a limit that a crack does not occur is referred to as crack resistance film thickness.
Here, the characteristics of the interlayer insulation film of a semiconductor device is better when a relative dielectric constant is lower, and the crack resistance film thickness is larger. The above described polymethyl siloxane film formed by the conventional process is 1200 nm in crack resistance film thickness when the relative dielectric constant is 2.8. Therefore, the polymethyl siloxane film formed by the conventional process has not been sufficient as characteristics of the interlayer insulation film of the semiconductor device.
Here, factors for producing the crack in the polymethyl siloxane film with the low relative dielectric constant formed by the conventional process will be described below. Such factors for producing the crack are that an internal stress caused by film contraction during bridge reaction occurs in the film with the low mechanical strength, and a thermal stress is applied during film formation.
In the case of the polymethyl siloxane film, the bridge reaction occurs due to dehydrate condensation. During the bridge reaction, a film contraction occurs, and after the formation of the film, the film contraction results in a residual stress of the film. In addition, during the bridge reaction due to heat treatment, the film contraction occurs while a material is thermally expanded. Thus, when this film is cooled to room temperature, contraction due to the temperature fall is applied. As a result, the residual stress of the film is further increased. In addition, a thermal stress applied by the temperature rise and fall causes an increase of bridge defects or voids, whereby the mechanical strength of the film that is originally weak is further weakened.
Further, recently, as a method for curing a coat film, for example, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-303190, there is proposed a method for coating a resin, partially evaporating a solvent, irradiating the coat film with high energy rays at room temperature or the like to cure the coat film, and further, applying a high temperature heat treatment to the coat film. According to the above described method, an insulation film with its excellent coat properties and flatness is obtained.
However, in order to form silica (silicon oxide film) with excellent coverage properties and flatness by the above described method, a resin is irradiated with high energy rays of 165 keV. Although the coat film can be cured by irradiation of such high energy rays at high levels, a network with its structure of a precursor in the coat film cannot be deformed. That is, with the above described method, the permittivity of the coat film cannot be reduced, and desired mechanical strength cannot be provided to the coat film. Further, the above publication fails to describe and suggest the reduction of permittivity of the coat film.
Further, in the method for forming the coat film using only one of heat treatment and electronic irradiation, there is a problem that a long time is required until the bridge reaction of the precursor ends. For example, it takes about 30 minutes to 1 hour until the bridge reaction of the precursor ends.
A method of manufacturing a semiconductor device comprises:
preparing a substrate to be treated; and
forming an insulation film above the substrate, which includes applying an insulation film raw material above the substrate, the insulation film raw material including a substance or a precursor of the substance, the insulation film comprising the substance, curing the insulation film raw material by irradiating an electron beam on the substrate while heating the substrate in a reactor chamber, changing at least one of parameter selected from the group consisting of pressure in the reactor chamber, temperature of the substrate, type of gas having the substrate exposed thereto, flow rate of gas introduced into the reactor chamber, position of the substrate, and quantity of electrons incident to the substrate per unit time when the electron beam is being irradiated on the substrate.